1. Field of the Invention
The present invention relates to a cyclone-type separator that utilizes a centrifugal force to separate solid matter from liquid coolants such as cutting fluid and grinding fluid for use in machine tools. More particularly, the invention relates to a structure that prevents liquid coolants from bubbling after foreign matter has been removed from them.
2. Description of the Related Art
In the process of cutting metal work pieces, a water-soluble liquid coolant composed mainly of much water is used to increase the lifetime of the tools, to enhance the precision of cutting and to remove chips fast. A water-soluble liquid coolant of this type is used over again. Hence, solid matter such as chips and metal particles should be quickly removed from the liquid coolant.
Known hitherto as a means for removing such matter is a cyclone-type separator. The cyclone-type separator comprises a main body, an inlet-port unit, a clean room, and a communication pipe. The main body has a discharge port in its lower end. The inlet-port unit introduces a dirty liquid coolant containing solid matter, into the main body. The clean room is provided in the upper end of the main body. The communication pipe guides the liquid coolant cleaned in the main body, into the clean room.
The main body is a conical hollow body whose diameter gradually decreases toward the discharge port. The inlet-port unit is provided in the upper end of the main body and injects the dirty liquid coolant into the main body. The dirty liquid coolant falls along the inner surface of the main body, in the form of an eddy stream. The eddy stream of coolant, thus generated in the main body, provides a centrifugal force. The centrifugal force separates the foreign matter from the liquid coolant. The foreign matter separated fall along the inner surface of the main body and is discharged from the main body through the discharge port.
The eddy stream of the coolant, falling along the inner surface of the main body, starts flowing upwards near the discharge port. That is, an upward eddy stream develops on the centerline of the main body, moving from the discharge port toward the clean room. The upward eddy stream includes a columnar air layer and a clean coolant layer. The columnar air layer passes through the communication pipe, reaching the clean room. The clean coolant layer rises along the circumferential surface of the columnar air layer.
The liquid coolant cleaned in the main body is guided into the clean room, along with the upward eddy stream, and thence into a coolant tank.
In the conventional cyclone-type separator, the columnar air layer and the coolant layer surrounding this air layer move upwards along the centerline of the main body, without mixing with each other. They move through the communication pipe, reaching the clean room.
In the conventional cyclone-type separator, an outlet port located at the downstream end of the communication pipe opens directly to the clean room. Inevitably, the air layer and the coolant layer mix with each other. That is, air mingles into the liquid coolant.
Consequently, the liquid coolant violently bubbles in the clean room, forming a great amount of foam. The foam enters the coolant tank as the liquid coolant flows into the tank. The coolant tank is inevitably filled with the foam, which may overflow the coolant tank.
To prevent the overflowing, de-foaming agent is added to the liquid coolant that has been cleaned, or a device dedicated to de-foaming is provided outside the main body.
As generally known, however, the de-foaming agent is a factor that degrades the cooling efficiency of the liquid coolant. A repeated use of the liquid coolant containing the de-foaming agent may lead to poor cutting results or may shorten the lifetime of the tools.
If a device for de-foaming the coolant is used, the system that reuses the liquid coolant will be a large-scale one, requiring a high operating cost and a large installation space.